The one "flaw" of Libertarianism is that because we base so much around the NAP, Abortion becomes an "unsolveable" issue depending on your interpretation of "life".

If fetus = life then they have the right to non-aggression, therefore pro-life.
If birth = life then until birth only the mother has the right to non-aggression. If the baby is considered aggressive (not literally, as in detrimental to the mother's life in any capacity) then pro-choice.

Democrats believe in Women's right to choice, so they are always in favor of the mother over the fetus, thereby always pro-choice.
Republicans are generally "morally guided" (i.e. Religious) and therefore usually consider the fetus to contain a soul and therefore be alive, thereby pro-life.

My personal opinion is that Libertarianism should focus on the government's ability for overreach, not the moral dilemma (for all other topics we say "your moral issues don't get to affect my choices").

Voluntary abortion by the Mother seems the most appropriate. If the government can enforce mandatory abortions, you get eugenics. If the government can enforce a ban on abortions, you get a black market and a societal net negative due to the quality of life generally becoming poor for the mother and child. The more conspiracy theory of banned abortions is also potential eugenics (ie. forced insemination, but that's pretty far-out).